Originally Posted by ALEX.

OP: "What brake fluid should I be running?"

P-WRX: "Purchase a new car".

Errr let's take a step back, coz that really escalated quickly.

Brods just get the car you have to a simple position where you can run around RAC or Barbs without having to head home early. Do some track days and start learning your driving style, the weaknesses in the car, and discover what is an important upgrade to you (more power? better handling? something that's not even a WRX?)
After a number of events you may well discover that you actually only want to do a couple of track events per year — good thing you didn't buy the 2005 STi which is now an overkill daily! OR you may discover that you're in love with this stuff and want to go buy a dedicated race car.

EDIT: started typing a reply when people were suggesting STis; came back finished off when everyone started going 'whoa slow down there Nelly'. Now I look like I missed the boat. Like usual [emoji14]

Get out there and see for yourself how you go!